Hey all.

I have a rather strange problem right now.

When I connect my HTPC to a Barco projector it's almost as if v-hold breaks on the Barco.

I suspect it may be because I use rather long BNC cables to the projectors.
Going from the HTPC to a NEC 6010 switcher and then via 25 meter long BNC cables to the projector.

I have tested several different projectors and all later model Barco's behave the same.

When I just have the desktop running no matter what resolution the picture is steady but if I start a movie the picture starts behaving erratically bouncing and rolling on the screen.
This almost stops when I press pause.
I have tested some Electrohomes and they all work just fine. No bouncing or anything except for when I try 1080p@48hz then picture is very slightly bouncy.

HOWEVER, and this is the strange part.
If I run wmv-files the picture is steady on the Barco's?!

I guess it may have something to do with the voltage that the graphics card is capable to send out and that Barco requires a stronger signal to sync to?
but that doesn't explain that SOME movies plays fine or does it?

Any thought on this?

I have the exact issue on my Barco Data 808s from my HTPC with a 7600GT card. My cables are shorter than yours (probably about 10-12 meters if my convesion is right) and I go through a PC1271 switcher (the latter which is forcing negative sync which Barcos like). Don't ask me why, but removing the V sync cable "fixes" the problem. Oh, this only occured at higher resolutions like 1080i and 960p. It was fine at 720p and lower.

There's a setting in the Nvidia window settings to force Neg sync.

Yep, it's positive sync issue.

Nvidia drivers have application controlled vertical sync as default, so that will explain why some player softwares or formats work fine and some are not...

Try to chance syncs to negative using classic advanced timing settings. Adjustments should stay better in register, if only one monitor is connected when changing. It could take few try to find driver version that would keep custom settings properly or you have to use Powerstrip.

I will play around a bit, but in my case, the PC1271 switcher is configured to force (convert) to negative sync so I don't think it is a pos/neg sync issue in my case, unless the jumper on my PC1271 switcher does not work. I have powerstrip so it will be easy to force negative sync at the card.

An update to this thread.

I tested with another HTPC running an 8800GTX.

It seems that the newer drivers from NVIDIA could be the problem.
NVIDIA seems to have screwed up the sync only outputting positive sync on the newer drivers because the only resolution I can get stable on one of the Barco 808LC I have setup in my theatre right now is 1024x768 and that is a resolution which uses positive sync.
I tried changing this with power strip but to no avail. The advanced timings always defaults to 640 x 480 and you can't change anything no matter what resolution I try at.
The picture is just rolling at anything higher than 1024x768.

Think an Extron interface would help?
Any recommendations?

How about Extron RGB 202xi?

Or what about this one?

Extron RGB 202 Rxi VTG
http://www.extron.de/product/img-lg/rgb202rxi-lg.jpg

I think you should try different nVidia driver versions until you find one that will allow you to set for neg. sync as Ile suggested.

Hmm how did I miss that suggestion.
Sure I will test that too.

Have no idea what nvidia has done lately (to some extent ATI as well) but their drivers seems to contain more bugs or different bugs between each version.
Just upgraded my HTPC and got an ATI card because nvidia doesn't work with powerstrip anymore :(
Way to go nvidia.